Abstract
Three types of self-assembled monolayers (SAMs) were prepared on metals and oxidized metals. They are an alkanethiol SAM chemically adsorbed on Cu and Fe, a benzene derivative SAM adsorbed on Fe by the formation of an Fe-C covalent bond and a carboxylate ion SAM chemisorbed on the surfaces of passivated Fe and hydrated Ce2O3 layer-coated Zn. Ultrathin (nm order thickness), ordered (self-assembly) and interconnected (two-dimensional polymer) protective coatings were synthesized by chemical modification of the SAMs adsorbed on metals and oxidized metals with silane coupling agents. The protective effects of these coatings on corrosion of substrate metals and passive film breakdown in oxygenated neutral solutions are summarized in this paper. The protective efficiency of the polymer coating on Cu in aerated 0.5 M Na2SO4 was extremely high, 99.3% at 1 h of the immersion time but decreased markedly after 20 h. The polymer coating of the benzene derivative SAM protected Fe from corrosion in the long range of the immersion time. Complete protection against corrosion of Fe was accomplished by coverage of a passivated Fe electrode with the two-dimensional polymer coating in the solutions, unless the passive film was broken down.
